Muscle Cramps Associated with Vincristine Therapy

The course of vincristine-induced neuropathy was evaluated in 14 patients who developed muscle cramps during chemotherapy. Cramps were noticed between 3 days and 4 months after the initiation of vincristine and following a cumulative dose of 1-9.4 mg/m2 (median 3.1 mg/m2). All patients reported daytime cramps and only 4 experienced nocturnal cramps. The lower extremities were involved in 11/14 and the upper extremities in 10/14 patients. Duration of cramps ranged from 1 to greater than 9 months. Physical examination revealed signs of peripheral neuropathy in all patients. Cramps were the first symptom of neurotoxicity in 4 patients. Other symptoms were noted in all patients, but only 3 had motor manifestations other than muscle cramps. Although symptoms of neuropathy tended to persist for several months, a rapid symptomatic improvement was noticed after withdrawal of vincristine. We conclude that vincristine-induced muscle cramps are not necessarily associated with severe neurotoxicity and should not automatically indicate interruption of therapy.